Support is requested from the Instrumentation Section of the Physiology and Biomedical Engineering Program of NIGMS for continuation of a broadly based program of biomedically oriented electron-spin-resonance (ESR) instrumental development. Pulse or time-domain techniques are emphasized. A high-speed data acquisition system has been developed that is 30 times faster than has ever before been achieved. It is computer controllable and the output is computer interfaced. Many experiments are proposed based on this instrument. A new but closely related instrument is being developed that will serve as a general purpose next generation of ESR spectrometer with substantially improved sensitivity. In an unrelated development program, new microwave bridges are being developed based on the recent availability of broad-band components. The biomedical thrust throughout the proposal is two-fold using these approaches on (1) nitroxide radical spin-labeled systems in order to gather improved information on motion of biomolecules and (2) on transition metals occurring singly or in multi-center sites in enzymes in order to understand electron transport and other oxidation-reduction reactions in better detail.